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PHOTOMOD 6.0
Task 3. We have photomaterial with calibrated crosses on it, we need to compensate
systematic metric scanner errors and errors of photomaterial, assuming that correct
coordinate of crosses are known.
Note. For typical flatbed scanners errors can be compensated if grid period is no more than
1 sm.
Order of operations:
1. scan photomaterial - file with raster image is created (e.g. image.bmp );
2. input manually (or import) table with correct coordinates of crosses, save it to file (e.g.
image.sct);
3. using data from image.bmp and table from image.sct create scanner‟s disturbances
field (this field is the sum of scanner and photomaterial errors), save it to image.etm;
4. transform raster data (file image.bmp), using field from file master.etm selecting the
same reference point. File with corrected image (e.g. newimage.bmp) is created
Task 4. We have calibrated material and photomaterial with calibrated crosses on it, we
need to compensate systematic metric scanner errors and errors of photomaterial, assuming
that correct coordinates of crosses are known.
Note 1. This task can arise if we have calibrated material with small grid period and
photomaterial with large grid period. For typical flatbed scanners errors can be compensated
if grid period is no more than 1 sm. The less the period the better results can be obtained.
Note 2. It is required that there should be some fixed (on scanner‟s plane) object on both
raster images, or scanned area should be the same in both scans (in scanner‟s coordinate
system) (see Appendix F. Recommendations for scanning).
Note 3. Calibrated material and photomaterial must be scanned with the same resolution.
Order of operations:
1. scan calibrated material - file with calibrated raster image is created (e.g. master.bmp );
2. scan photomaterial - file with raster image is created (e.g. image.bmp );
3. using data from master.bmp create scanner‟s disturbances field, save it to master.etm.
Do not forget to select reference point - characteristic point correspondent to some
fixed point (see. Note 1 above);
4. transform raster data (file image.bmp), using field from file master.etm selecting the
same reference point. File with corrected scanner errors (e.g. image_tr.bmp) is created;
5. input manually (or import) table with correct coordinates of crosses, save it to file (e.g.
image.sct);
6. using data from file with transformed raster image image_tr.bmp create disturbances
field of photomaterial taking into account table image.sct, save field in file image_tr.etm;
7. transform raster data (file image_tr.bmp), using field from file image_tr.etm. File with
corrected errors (e.g. newimage.bmp) is created;
Task 5. We have non-ideal calibrated material and photomaterial, we need to compensate
systematic metric scanner errors, assuming that correct coordinates of crosses on calibrated
material are known.
Note 1. To obtain correct coordinates of crosses on non-ideal calibrated material:
1. scan calibrated material on photogrammetric scanner. File with raster image (e.g.
ideal.bmp) is created;
2. using data from ideal.bmp create disturbances field, save it to ideal.etm;
3. create table with correct coordinates of crosses on calibrated material using import from
.etm with file ideal.etm, save table in a file (e.g. ideal.sct);
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